1. Field of the Invention
The present invention relates in general to adaptively determining the presence of a RF signal received by a receiver upon entering a wake state, and more specifically, to extending the period of time of the wake state for determining the presence of the RF signal.
2. Description of the Related Art
RF receivers in vehicle control modules typically cycle between a sleep state and wake state for conserving power while monitoring for the presence of incoming signals. When transitioning from the sleep state to the wake state, power is supplied only to those components that are necessary to determine if a RF signal is present. A low current power source is typically provided to those components for detecting the presence of the received RF signal. This allows for a minimum amount of power consumption while detecting the presence of a valid signal. If a determination is made that the signal is present, then those components of the vehicle control module that are required to process the received signal and perform any control action are fully powered.
The time allocated to detect a RF signal is minimal due to the duty cycling between the sleep state and the awake state. This time allocation for detecting the RF signal must be of a sufficient duration to receive a minimum number of data pulses for determining whether a valid signal is present. An additional concern is the detection of a RF signal from that of noise. Some data protocols include a quiet time where no data transmission occurs between a transmission of data packets. This quiet time may produce noise in the absence of a transmitted signal due to the tuning of the RF circuitry. As a result, the control module may possibly wake up to noise or wake up at a time when no signal is being transmitted or noise is present. Noise on a circuit may resemble that of a data pulse. Furthermore, the control module may wake up during the transmission and only receive a portion of the transmitted signal. Having received less than a minimum amount of transmitted data pulses required to analyze and make a determination that a RF signal is present the control module would enter the sleep state not realizing that a RF signal is being transmitted.